Sunday, July 6, 2014

Why Jesus died many times for our sins

St. Augustine was sure that Jesus died just once for our sins. However, Jesus died not only in our particular universe but also in many other parallel universes that are as real as ours.

Let’s explore the chain of reasoning behind this claim. One assumption is that whether a particular parallel universe exists falls within the field of astrophysics, not theology nor logic.

Astrophysics’ well-accepted Big Bang theory with eternal inflation implies a multiverse containing an unlimited number of parallel universes obeying the same scientific laws as in our particular universe. These other universes (which the physicist Max Tegmark calls Type 1 universes) are distant parts of physical reality. They are not abstract objects. Some contain flesh and blood beings.

Parallel universes are not parallel to anything. They are very similar to what David Lewis called possible worlds, but they aren’t the same because his possible worlds must be spatiotemporally disconnected from each other.

I cannot state specific criteria for transuniverse identity, but we do need the assumption that, in a universe, personal identity (whatever it is) supervenes on the physical realm. That is, a person can’t change without something physical changing. It is also reasonable to require that in any parallel universe in which Jesus exists he has Mary and Joseph as parents.

The claim that Jesus in our universe is identical to Jesus in another universe does conflict with the intuitively plausible metaphysical principle that a physical object is not wholly in two places at once. This principle is useful to accept in our ordinary experience, but it is not accepted in contemporary physics. The Schrödinger equation of quantum field theory describes the extent to which a particle is wholly in many places at once. This is why physicists prefer to say the nucleus of a hydrogen atom is surrounded by an electron cloud rather than by an electron. In the double-slit interference experiment, a single particle goes through two slits at the same time. So, the metaphysical principle should not be used a priori to refute our claim about the transuniverse identity of Jesus.

Our universe is the product of our Big Bang that occurred 13.8 billion years ago. It is approximately that part of physical reality we can observe, which is an expanding sphere with the Earth at the center, having a radius of 13.8 billion light years.

Our universe once was a tiny bit of explosively inflating material. The energy causing the inflation was transformed into a dense gas of expanding hot radiation. This expansion has never stopped. But with expansion came cooling, and this allowed individual material particles to condense from the cooling radiation and eventually to clump into atoms and stars and then into Jesus.

The other Type 1 parallel universes have their own Big Bangs, but they are currently not observable from Earth. However, they are expanding and might eventually penetrate each other. But, they might not. It all depends on whether inflation of dark energy is creating intervening space among the universes faster than the universes can expand toward each other. Scientists don’t have a clear understanding of which is the case.

Why trust the Big Bang theory with eternal inflation? Is it even scientific, or is it mere metaphysical speculation? The crude answer is that the theory has no better competitors, and it is has been indirectly tested successfully. Its testable implications are, for example, that the results of measuring cosmic microwave-background radiation reaching Earth should have certain specific quantitative features. These features have been discovered—some only in the last five years. The theory also implies a multiverse of parallel universes having our known laws of science but perhaps different histories. If we accept a theory for its testable implications, then it would be a philosophical mistake not to accept its other implications.

One other important assumption being made is that the cosmic microwave-background experiments have not detected any overall curvature in our universe because our universe is in fact not curved. Our universe being curved but finite is also consistent with all our observations. Similarly, if you are standing on a very large globe, it can look flat to you. If our 3-D universe is finite but curved like the surface of a 4-D hypersphere, then space would be extremely large with a very small curvature, but there would be only a finite number of parallel universes, and the argument about Jesus would break down. The most common assumption now among astrophysicists is that our universe is in fact infinite, the multiverse is infinite, and matter is approximately uniformly distributed throughout the multiverse. As Max Tegmark has pointed out, twenty years ago there were many astrophysicists opposed to parallel universes. They would say, “The idea is ridiculous, and I hate it.” Now, there are few opponents of parallel universes, and they say, “I hate it.”

Having established that there are infinitely many parallel universes with the same laws but perhaps different histories, let’s return to the issue of whether Jesus died in more than one of them. One implication of the Big Bang theory with eternal inflation is that some universes are exact duplicates of each other. Here is why. If you shuffle a deck of playing cards enough times, then eventually you will have duplicate orderings. The duplicate orderings are the same, not just “David Lewis counterparts.” Similarly, if you have enough finite universes, which are just patterns of elementary particles, and each has a finite number of possible quantum states, then every universe has an infinite number of duplicates.

One controversial assumption used here is the holographic principle: Even if spacetime were continuous, it is effectively discrete or pixilated at the Planck level. This means that it can make no effective difference to anything if an object is at position x meters as opposed to position x + 10 -35 meters.

This completes the analysis of the chain of reasoning for why Jesus died more than once for our sins. Have you noticed any weak links?

14 comments:

Brad, this is very interesting and fun, thanks. I could talk to you about this all day, but I'll confine my question to the idea that a particle can not be in two places at once.

First, I wonder what it means to say that "The Schrödinger equation of quantum field theory describes the extent to which a particle is wholly in many places at once." If someone asks. Is particle P wholly at location L? The answer "To some extent," seems to mean the same thing as "No," (on the assumption that some extent is less then wholly." My understanding of the Schrödinger equation is that it tells us the probability that a particle is at any particular location, with the meaning of that statement varying depending on the resolution of the measurement problem you favor. Your remark seems to me to be most consistent with the Many Worlds Interpretation, where the probabilities represented in the Schrödinger equation may reflect the distinct worlds that actually exist. However, you do not make any reference to the Many Worlds Interpretation, and as far as I know, physicists are currently not at all sure what the relation is between the Multiverse and Many Worlds (though Sean Carroll thinks they could be the same:

The other question I have is whether we really need to go this route at all. Kant, I believe, would have said that the idea that an object can't be wholly in two places at once is an a priori intuition, and therefore necessarily the case. But he said the same thing about 3-D spacetime, and he was just wrong. So why not simply respond that this intuition can denied without contradiction, and since the denial fits a very good physical theory, we should deny it? Specifically, why not just say that a particle can be wholly present in only one position in a single universe, but it can be wholly present in multiple positions in multiple universes?

Kant’s intuition can be denied without contradiction, and the denial fits well with current physical theory. But I wouldn’t want to draw your conclusion that “why not just say that a particle can be wholly present in only one position in a single universe.” What fits best with physical theory is that a particle can be in multiple locations in a single universe and also in multiple locations across universes. I mentioned quantum mechanics in my blog post just to make the point that all experts agree that a particle can be in two locations at once in our own universe, despite the violation of common sense. You are right that the Schrödinger equation “tells us the probability that a particle is at any particular location,” but don’t assume from this that there is a definite location it has. Schrödinger abandoned the idea that a particle has a definite location in our universe. Niels Bohr’s Copenhagen Interpretation says a particle is at a definite location “to some extent,” meaning the particle is not wholly at any place when unobserved. The italics is what is special about a Copenhagen Interpretation. The Schrödinger equation tell us that particles are here and there at once; a particle is always in a “superposition” of here and there when it is not being observed. Bohr said, “No reality without observation!” I am not that much of an idealist and happen to believe the Copenhagen Interpretation is incorrect because I believe the wave function never collapses. This is the position of Hugh Everett. I was not promoting Everett’s Many Worlds Interpretation of quantum mechanics in my blog post, but it is a reasonable position, though still controversial. In the multiverse theory that I was promoting, the many parallel universes are far away; in the Many Worlds theory the universes are disconnected from our space and are neither near nor far. I think if Einstein were alive today he’d reject the Copenhagen Interpretation and go with the Many Worlds Interpretation.

Brad, thanks for that reply. There is a difference, don't you think, between the idea that a particle is not wholly at any place at one time and the idea that a particle is wholly at many places at once? The first formulation seems right to me, the second I have trouble grasping.

I like the Everett interpretation, too, especially because of the way it seems to take the mystery out of EPR, but I actually do not quite understand exactly how it interprets the Schrödinger equation. On the basis of what I know it seems to me that it is a kind of hidden variable theory in which what we don't know is, not the actual, definite location of the particle in a particular universe, but whether we occupy a universe in which the particle is definitely in this position or definitely in that one. In other words, on the Everett interpretation, there is no collapse of the wave function, so what the wave function tells us is the probability that we are in a certain kind of universe, but this seems compatible with the view that particles have definite locations in every universe.. Is this wrong-headed and can you shed anymore light on this? (I know it is not central to your post.)

Randy, in quantum mechanics when talking about point particles such as electrons in a single universe, I believe it’s not helpful to emphasize a difference between not being wholly at any place at one time and being wholly at many places at once. That’s because a particle has no definite location (when it is not measured, according to the Copenhagen Interpretation). Now I used this example, with its implicit endorsement of the Copenhagen Interpretation, in order to suggest that physicists have for a long time been willing to say a particle can be in two places at once within an atom. However, I don’t endorse the Copenhagen Interpretation myself and prefer the Everett Interpretation, which describes the world as you say in your comments. The Everett many-worlds interpretation is compatible with the view that particles have definite locations in every universe, as you say. And, as you say, this removes the mystery from the EPR paradox (although it adds in mystery in another way—by introducing the unintuitive concept of parallel universes). That is the very reason why I commented that Einstein would approve of this interpretation over the Copenhagen interpretation if he were alive today. However, the Everett interpretation is also compatible with the claim that a particle can have two locations—that the particle can be wholly present in two places, namely having locations in two universes. In the last ten years, the Copenhagen Interpretation has fallen out of favor.

Thanks Brad for the thoughtful and fun post. I always learn something from you when you talk physics. I am not competent to comment on the physics so I will accept whatever you say on that, for the sake of argument. But I think the physics is a smokescreen. I avoid any conceptual or theological issues surrounding the nature of Jesus, the death of any god, child-sacrifice, etc. These too are not relevant, just like whether death is a singular or permanent event for Jesus or anybody is also tangential. I see two problems. (1) I think there is an implication failure perhaps due to ambiguity. That the same person with counterparts in many (or even all) other worlds dies could be true, and yet it could be false that each one (or any one) dies many times. Possible worlds or parallel worlds talk doesn’t even support the notion that, in any world where Jesus exists, that Jesus even dies once in all of them. (2) Some kind of quantifier shift error threatens. The general point you raise, that some guy died many times, is possible, sort of like the universe could have undergone an eternal series of crunches and expansions is possible. However, this fails to support any particular Jesus-story or Big-Bang story. It does not entail that anybody actually died many times in any given world. So “(there exists a) Jesus (who) died more than once for our sins” could be false even if “all Jesuses die in any world where any Jesus exists”. Again the latter claim is false, because there is a possible world or parallel universe where he does not die, or some worlds where his counterpart does not. So I suspect that your presumption is false, but again I don’t get the physics: “Similarly, if you have enough finite universes, which are just patterns of elementary particles, and each has a finite number of possible quantum states, then every universe has an infinite number of duplicates.” OK, I am not sure what this proves, but isn’t it possible that you could have an infinite series of arrangements of particles (with a finite number of possible states) and never get any duplicates? To presume this, I think, is to presume that whatever is possible is inevitable. It was dubious for Nietzsche to assume this in his doctrine of Eternal Recurrence and it is also dubious to presume it here. In short, Jesus died (or really did not) in this world, once, and that’s it. If you want to run worlds in parallel or series, the problem of ambiguity remains. I do not presume that names (proper or otherwise) are rigid-designators, so this could be part of my problem with understanding your argument.

Scott, you’ve made some very interesting comments. I agree with some and disagree with some others.

You said, “isn’t it possible that you could have an infinite series of arrangements of particles (with a finite number of possible states) and never get any duplicates?” I believe the answer is “no.” You might shuffle a deck of cards an infinite number of times and still never get it back to its original order. But if you shuffle it a very large, finite number of times you are absolutely sure of getting two orderings that are the same. You don’t even need to shuffle it an infinite number of times.

You are right that it’s mathematically possible there won’t be any duplicates of our universe even if an actually infinite number of parallel universes are generated. However, if you start shuffling with the deck in a certain order, then as you shuffle more and more, the probability of getting it back to the original order gets higher and higher and approaches one in the limit of an infinite number of shuffles. This is an implication of a theorem in probability theory, assuming random shuffles. I’d bet my life that you’ll get the deck back to its original order eventually. So, to speak epistemologically, I’d say I know you’ll produce the duplicate. Ditto for there being multiple Jesuses in the multiverse, assuming random generation of parallel universes. The assumption I left out in my original posting was that the generation of parallel universes is random.

In most parallel universes there won’t be a Jesus, nor even homo sapiens. I hope you agree with me that solid historical evidence establishes that there was a Jesus in our universe about two millennia ago. In my blog I chose to talk about Jesus mere as an attention-getter. I could have made the same points talking about Abraham Lincoln.

Randy, here’s another thought about your recommendation that we say a particle is wholly present at one place in one universe. In the two-slit diffraction experiment, if you fire particles very slowly at a target, then we can show that the particle goes through both slits and interferes with “itself.” You wouldn't want to say the particle wasn’t “wholly present” when it went through the left slit. It's not like the particle's left half went through the left slit, right? But at the same time the particle was also going through the right slit, even though there was exactly one particle fired at the slits. So, the particle was wholly present in two places at once.

Brad, do we want to use the term 'particle' here? I thought the point here is that when, say, an electron interferes with itself it is because it is not behaving as a particle at all, but as a wave. If it were behaving as a particle, then, by definition, it would have to pass through one slit or the other, right?

Is there a difference between how Bohr and Everett account for this experiment? As I understand it, Bohr says that the act of measurement collapses the wave function, and forces the entity to behave as a particle. But on the Many Worlds interpretation there is no collapse of the wave function, so why the difference when it is measured and when it is not? Why doesn't the entity continue to behave as a wave?

Randy, you are raising deep issues about the philosophy of quantum mechanics. Yes, it is better not to use the word “particle” when we are talking about wave interference. However, even if we were to stick to the classical Copenhagen Interpretation, its principle of complementarity allows the two-slit experiment to be considered either as a wave or as a particle experiment but not at the same time.

So, let’s use the word “particle.” When we consider it as a particle experiment, then the particle must go through both slits simultaneously, yet hit the screen behind it at ONE place. It is wholly in two places at once as it goes through the screen. Richard Feynman said this is the essence of quantum weirdness.

You asked, “on the Many Worlds interpretation there is no collapse of the wave function, so why the difference when it is measured and when it is not? One answer is that measurement produces quantum decoherence.

You then asked, “Why doesn’t the entity continue to behave as a wave?” The answer is that it does.

My blog post is basically reporting on the views of Max Tegmark from his 2014 book Our Mathematical Universe. He is leader of the quantum decoherence idea. According to Tegmark, the reason why there is such a big difference between measured and unmeasured particles is quantum decoherence or mixing with lots of other particles, not intrusion of consciousness as the Copenhagen people believe. According to Niels Bohr’s Copenhagen Interpretation of quantum mechanics, particles behave strangely only because they are unmeasured by a conscious being. In Schrödinger’s thought experiment in which there’s a 50-50 chance of the release of cyanide gas within ten minutes of the room being sealed, the Copenhagen people say Schrödinger’s cat is both alive and dead in the room because it is now ten minutes later and no conscious being has yet looked into the room and become aware of the situation. But then someone looks in and the cat is, say, still alive, and this looking collapses the wave function and that is why we never observe macroscopic objects in quantum superposition. Observing always causes collapse.

Wrong, says Tegmark. Consciousness is not what collapses the wave function. It never collapses, and consciousness is unimportant. Instead what is important about measurement removing the weirdness is that the object measured gets entangled with the many objects in the measuring tools. Seeing requires bouncing photon objects off the measured object, which destroys quantum superposition. This destruction via getting entangled with many other objects is what Tegmark calls quantum decoherence. According to Tegmark, the reason why we never see macroscopic objects such as cows and people in two places at once is not because they are macroscopic, and not because they are observed, as the Copenhagen Interpretation hypothesizes, but rather because it is too hard to isolate them from other particles and prevent decoherence. I do not understand this process very well, but the point seems to be that it is an object’s interaction with other particles that destroys its quantum superposition via the process of quantum decoherence.

But Tegmark’s interpretation of quantum mechanics is not yet standard, so in my original post I did not mention it.

Brad, thanks, that's very helpful. Charles Seife's book Decoding the Universe has an approving chapter on Tegmark's decoherence explanation. For him, the key conceptual move is to think of information as something that exists in the world, and measurement as the transfer of information from one place to another. Once you do that, there is no problem thinking of nature itself as constantly making measurements. Do you recommend Tegmark's book?

Brad: (This is Cliff, now in the La-La land of retirement.) Interesting as the multiple universe theory is, isn't it the case that there is no way to empirically confirm it? Can we make the jump from: Quantum theory is well-confirmed for our universe and quantum theory implies there are multiple universes, therefore there must be multiple universes? To me that's seems to stretch the idea of empirical confirmation too far.

Cliff, I worry about all those questions, too, and am not yet convinced of the claim that Jesus died many times for our sins. You have a fine pragmatic attitude toward the issue. Since we can’t make predictions about other universes, that is something to worry about.

If there were no way to empirically confirm the claim that there exist alternative universes, then I wouldn’t believe it either, but there are ways to empirically confirm it—indirectly—because it provides good explanations of observations even if it can’t provide predictions that can be tested. You would say this indirect confirmation is too indirect and it stretches the idea of empirical confirmation too far. Proponents of alternative universes say it is time for science to change and accept this stretching.

Here are some relevant quotations from Leonard Susskind in his 2006 book The Cosmic Landscape. “On the theoretical side, an outgrowth of inflationary theory called Eternal Inflation is demanding that the world be a megaverse, full of pocket universes that have bubbled up out of inflating space, like bubbles in an uncorked bottle of champagne." (p. 21)

He calls alternative universes “pocket universes,” and he calls the Level I Multiverse the “megaverse.”

"There is very little doubt that we are embedded in a vastly bigger megaverse." (21-2)

“But certainly the critics are correct that in practice, for the foreseeable future, we are stuck in our own pocket with no possibility of directly observing other ones. Like quark theory, the confirmation will not be direct and will rely on a great deal of theory.” (196)

As for rigid philosophical rules, it would be the height of stupidity to dismiss a possibility just because it breaks some philosophers’s dictum about falsifiability. …Just as general are always fight the last war, philosophers are always parsing the last scientific revolution.” (196)